This invention relates to an engine injection system and more particularly to an improved fuel supply arrangement for supplying the fuel to the injectors of a multi-cylinder engine.
The use of fuel injection for operating internal combustion engines and to provide the charge-forming system for such engines is being resorted to for a variety of reasons. Not the least of these is the possibility of improved fuel economy and also of better exhaust emission control. However, in some regards the fuel injection system is more complicated than other forms of charge-forming systems and particularly where multiple cylinder engines are involved.
With multiple cylinder engines, it is generally the practice to try to position the fuel injectors so they are all in an in-line relationship. With V-type engines, the fuel injectors associated with the individual cylinder banks are aligned with each other in a common type of construction. However, this generally means that the fuel is supplied to all of the aligned injectors through a common fuel rail.
A difficulty with such an arrangement is that at times the fuel injectors of adjacent firing cylinders may have overlap in their time periods of injection or they may be closely spaced so that the injection of fuel from one injector can adversely affect the amount of fuel injected from the next firing injector.
This problem can be best understood by reference to FIG. 1 which is a graphical timing diagram showing a complete revolution of a six-cylinder, even firing, internal combustion engine operating on a two-stroke principal and having fuel injection. The timing of firing of the individual spark plugs is shown as is the duration of fuel injection under a high-load/high-speed condition. It will be seen that although the cylinders are set so as to fire at equal intervals. 60.degree. from each other the long duration of fuel injection causes some overlap in injection between adjacent firing cylinders.
If a common fuel rail supplies fuel to these adjacent firing cylinders, then, even though the pressure is regulated, there may be a drop off in the amount of fuel injected during the overlap period. This cylinder-to-cylinder variation may also occur even if there is no overlap if the timing of injections are close to each other as the pulses in the fuel rail may also have a similar effect. Also this makes simultaneous injection periods undesirable.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for a multi cylinder engine.
It is a further object of the invention to provide an improved multi cylinder fuel injection system and fuel supply arrangement therefor so that uniform fuel injection can be enjoyed under all engine running conditions.